1. Field of the Invention
This invention relates to a data regenerator for regenerating data included in an electric signal from a photoelectric converting section in an optical receiver, and to an optical receiver having the data regenerator.
2. Related Background Art
In recent years, an optical communication system for transmitting an optical signal for a long distance has been developed for practical use. The optical signal consists of a series of pulse. The signal is transmitted using an optical relay device. The relay device includes an optical receiver. The receiver includes a photoelectric converting device. When the receiver receives the optical signal, the signal is converted to an electric signal by the photoelectric converting device. Thereafter, the receiver regenerates pulse data from the electric signal. In the regeneration, a certain decision level is used to discriminate the level of the pulse waveform of the signal. The decision level is not limited to being the central level of the pulse waveform. The decision level changes according to various factors, such as the shape of the pulse waveform and a noise added to the signal.
In an optical communication system, the optimum decision level differs depending on a communication environment. For example, the optimum decision level differs according to a noise generated in the optical relay device or dispersion distortion caused by wavelength dispersion in a long-distance optical fiber. The difference in the decision level is noticeable between the systems for transmitting optical signals over long distances. In order to handle the variety of the decision level, the decision level need to be set manually for every optical communication systems. However, this method requires much expense in time and effort, and does not easily respond to subsequent change in the communication environment.
In order to overcome this problem, technology for enabling an optical receiver itself to set an optimum decision parameter without external control has been investigated. An example of the technology is disclosed in Japanese Patent Laid-open No. HEI 10-13396.